Chapter 620: Reverse card? Forget it
If the signal generation has been solved, what is left is the detection and processing of the signal. The detection is still certain, as long as the signal power is large enough.
Then in the end, it’s another one.
"But our technical means for signal processing are very weak, and there is basically not much we can do about the signal itself. As for the processed signal results, we can use your DJS-60D to calculate it, but it cannot solve the fundamental goal. Detection issues.”
Signal processing technology is the real stumbling block.
Regarding this, Gao Zhendong was not panicked.
"In this way, with a good signal source, we walk on two legs, walking on analog while thinking about digital. I know a little bit about both aspects."
In fact, for Gao Zhendong, what he knows better is digital signal processing, which he can directly and violently obtain some desired results by stacking computing power. To a certain extent, by stacking hardware mathematical co-processors, he has the Ready-made algorithms are easier than creating analog circuits.
However, there is an unsolved problem in digital signal processing, which is high-speed AD. Generally speaking, when the signal is converted from analog to digital, the sampling rate needs to be more than 10 times the signal frequency to obtain better waveform data.
This is a very serious challenge for existing devices, and it is very troublesome even if other signal preprocessing operations are performed first.
As for direct sampling and direct digital processing, although this kind of thing is cool, it is just a fantasy for current devices, so there is no need to consider it.
So Gao Zhendong’s idea is to walk on two legs. If digital processing cannot be done in a short time, it is also possible to use analog circuits for Doppler processing. At least the F-4J APG-59 uses analog Doppler processing. The effect is not bad.
At least it's much better than the MiG-23, and it's not too bad at being on the same level as the F-4J five years later.
Regarding the principle of radar, Gao Zhendong collected some information out of personal hobbies in his previous life, especially the PD radar, which is not the latest but is widely used. When everyone still hid the phased array, the content of PD technology was relatively unknown. Easier to find.
The knowledge from the technical environment decades later is really a dimensionality reduction blow now.
With the principles of radar and the corresponding simulation processing techniques, Gao Zhendong still has some knowledge. Don’t forget one thing, that is, courses such as signals and systems, and time and frequency domain analysis of signals were his professional courses in his previous life. .
With the knowledge from the past life and the brains of this life, it is not a problem to explain the principles clearly to everyone. With these targeted theoretical knowledge, I believe these comrades will have their own methods.
It's like the guy who does HIFI. He may not understand the real principles, but if you ask him to build a tent, he will do it very well.
Seeing that Gao Zhendong was confident, and considering that the National Defense Working Committee had already acquiesced to this radicalization, and even in order to wipe away the possible consequences of such radicalism, the National Defense Working Committee strongly retained the imitation work of RP-1.
These big guys are willing to take a gamble, so it's no big deal if he follows suit.
If PD fails, then it is not a problem to use the intermediate results of PD and retract it to make a low-profile radar with single pulse + moving target indication. What are you afraid of? This thing is definitely better than the imitation RP-1.
The traveling wave tube proposed by Gao Zhendong gave him great confidence. As the saying goes, miracles come with great power. Now that we have great power, we might as well look forward to miracles.
The comrades who bear the main responsibility are brave enough to fight hard. It would be too incompetent to shrink back. Moreover, they are not completely unprepared. Everything from equipment to theory has been considered.
Don't listen to what others say about being humble and "knowing something". In fact, it means "don't be afraid, I will teach you".
"Okay, in this case, we will follow the PD radar." Mr. Liu made up his mind. If this cross-generation can be achieved, it would be really great.
The young people who came with him were also gearing up. They were definitely the group that screamed and charged the most. If you want to do something like this, do it in a big way.
Seeing Gao Zhendong completely rejecting the plan that his group had been thinking about for a long time, they showed no sign of being unhappy at all, and they were still so energetic.
"General Engineer Gao, everything is almost done, then look at this antenna..."
Gao Zhendong burst out laughing, making Mr. Liu look confused. Is the antenna thing funny?
Gao Zhendong didn't know how to explain it. The main reason was that he remembered the famous joke in his previous life - the "card-reversing artifact" was coming, and he couldn't help it.
The inverted card artifact comes from the antenna structure used by Lao Maozi from the MiG-21 to the Su-27 - the inverted Cassegrain antenna. In fact, this thing is also used by others, such as John Bull's Tornado. , many marine radars are also used.
The reason why only Lao Maozi made this joke is mainly because we use this thing a lot, and we don’t use it well. Master 8’s card-reversing magic tool has not been developed for decades.
In addition, the Su-27's basic back-up radar is large and heavy, and its parameters look outrageous, but its actual BVR capabilities are at the bottom among our third-generation aircraft. Not to mention anything else, even the Fortune Block2 that I don't use can use it. Rub against him. So the rather unhappy domestic military fans gave him this nickname.
The reason why Gao Zhendongle came out is not because Mr. Liu used a reverse card antenna this time. In fact, it happened to be because it did not use a reverse card antenna, but used the reverse card's father-the Cassegrain antenna.
It is estimated that although the nose space is much larger, the high focal length ratio requirement of the parabolic antenna is still not good for combat, so he chose the Cassegrain antenna, which has a relatively low focal length ratio requirement.
However, the Cassegrain antenna was not actually used on fighter jets for a long time and was replaced by reverse antenna. The main reason was that the signal center was blocked and the side lobe level was high.
The reverse card solves the problem of the Cassegrain antenna. What is interesting is that if a comrade who does not know much about radar sees the complete reverse card antenna, there is a high probability that it will be mistaken for a phased array.
In fact, it is completely impossible to use this antenna as a phased array antenna. Instead, it is another type of antenna that can achieve phased array capabilities, and that is a flat slot antenna.
Although the flat plate gap looks like a flat plate, it is actually made up of many waveguides put together. It is a pile of independent tubes. If the signal part is well designed, the principle of the phased array can indeed be realized, but the number of units is limited. Maybe not too big.
Having said that, as a very popular antenna form in second-generation aircraft, the performance of the inverted card antenna is still good at this time. Before the birth of the flat slot antenna, this was considered one of the antenna structures for fighter aircraft with the best overall performance.
However, after using it in the 1990s and even after 2000, it began to fall behind. The second-generation machine's card reversal is a real magic tool, and the third-generation machine's still using the card reversal is a bit magical.
But the reverse card can really be used on PD radar. The antenna and radar system are not compatible.
Gao Zhendong couldn't explain Mr. Liu's puzzled look, so he had to get straight to the point: "Nothing, nothing, just thinking of something else. So, Mr. Liu, why don't we use an inverted Cassegrain antenna here?"
This is where Gao Zhendong is very confused. If I remember correctly, the RP-1 radar copied by Mr. Liu in front of him, the ranging radar installed in the middle of the air intake duct and with a ranging distance of "up to" 3 kilometers, is the reverse one. Ka, supposedly he shouldn't not know. Gao Zhendong had seen a photo of that thing in his previous life, and he could see it at a glance. The features were too obvious.
Mr. Liu smiled and said: "RP-1 is used as a reverse card. Its performance is too poor, so I used this one."
Gao Zhendong originally wanted to suggest using the reverse card first. After all, the radar performance of the RP-1 is poor and has nothing to do with the reverse card antenna. The reverse card is more suitable for use on fighter jets than Cassegrain. That thing is not worth watching. Yuan Yuan was purely a matter of skill and size, but when the words came to his lips, his heart moved and he still held back.
This matter will be discussed later. Anyway, whether you use the upright card or the reverse card now, it will have little impact in the end.
There are enough no's, no more is not good.
"Well, that's it...the antenna...let's just leave it like this for now." Gao Zhendong said vaguely.
Mr. Liu probably heard something interesting, but seeing that Gao Zhendong had no other expression, he just went ahead with it.
"Well, Chief Engineer Gao, I will correct this first and send it to the Defense Working Committee?" Mr. Liu, who had gained a lot, put away his notebook.
Gao Zhendong nodded: "Well, let's go as fast as possible. The AT-5 multi-purpose type is making good progress now. It would be a pity if we don't have a good radar in the end."
Judging from the feedback from the Porcelain Flying Factory, they are making good progress and so far it is generally going smoothly.
If R&D in later generations is extremely time-consuming, then in this era, R&D speed is relatively much faster, because the technology is not so complex, precise, and extreme, and the progress of research, manufacturing, and testing is much faster.
After sending Mr. Liu and the others away, Gao Zhendong opened a set of drawings.
If you just look at the picture of the shell, you can see that it is a rectangular box with a basically square cross-section and it doesn't look very big.
This is exactly what he and Mr. Liu mentioned just now, the traveling wave tube.
He has not found a traveling wave tube design that will reach the most advanced level in a few decades, but he can still find one that meets the conditions of the current era or is slightly ahead of its time.
The good thing about this thing is that it can trade volume for performance, but Gao Zhendong did not directly make it too big. He had some other ideas. One way to achieve miracles is to use force, but he has his own considerations as to how powerful it should be.
After checking it carefully, he bagged and sealed all the drawings, called the comrades in the confidential room of the No. 3 Factory, and asked him to send the drawings to the Defense Working Committee, and asked the comrades of the Defense Working Committee to choose the relevant ones. A professional factory will produce a batch of them on your behalf.
At the same time, Gao Zhendong specifically pointed out that the production plant of this thing has requirements for the personnel structure. In addition to meeting basic confidentiality requirements, it cannot have foreign comrades.
(End of chapter)